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Wise Coastal Practices for Sustainable Human Development Forum
Posted By: Bambang Radi
Date: Tuesday, 6 July 1999, at 11:24 a.m.
In Response To: The repercussions of salt extraction / Bhavnagar Bhal-India. (R. Sudarshana)
GROUNDWATER EXTRACTION AND LAND SUBSIDENCE : From April to June 1999, I did a study on 'Ground Water Salinity Related Impacts and Mitigation Plans in the Bhavnagar Region,' which is situated on the coast of Gujarat. The study found that this area has very heavy salinity, with a chloride content of more than 1000 mg/L. Moreover, the salt- water intrusion has reached 25 km inland.
Unfortunately, in his observations Dr. R Sudarshana does not deal with the problem of land subsidence. This process occurs when groundwater is pumped from a confined sand and gravel aquifer, which is overlain by highly compressible clays. As pressure within the aquifer drops, the aquifer materials and the overlaying clays gradually become compacted.
The consequences of land subsidence include: structural damage to buildings, roads and other infrastructure; malfunctioning water and sewer systems; and in coastal areas, increased risk of flooding.
WHAT IS THE FUTURE OF BHAVNAGAR BHAL? Following an increase in the market price of salt, salt-pans were established around Bhavnagar City. The groundwater (from a depth of 122 m) is pumped to exploit salt resources. If ground water withdrawal exceeds a maximum limit, the aquifer levels of the coastal area will decline, accelerating saltwater intrusion. The intrusion of salt water will rise approximately 40 m for every metre dropped in the water table. The inhabitants of Bhavnagar Bhal depend on the Bhavnagar City fresh water supply, which is distributed by water tank truck.
In Bhavnagar City an examination was carried out to determine the chloride content in its water supply. Results show that the groundwater in this region has been affected by salt water intrusion. Likewise, the depletion of Bortalav Lake water indicates an over exploitation of groundwater in this city.
Bhavnagar, a city with 600,000 inhabitants, is in danger of salt-water intrusion.
Salt accumulation does not take place in sandy soil probably due to Global Salt Circulation. The irrigation of sea water causes accumulated salt to be washed to deeper zones and the presence of proper underground drainage carries the salt back to the sea, where primary ground water moves in a horizontal or lateral direction at a velocity of approximately 1 to 500 m/year. I think that the problem in Bhavnagar Bhal is soil saturation caused by using the saline water for irrigation. This has led to increased groundwater salinity. Over exploitation of ground water for salt-pan activities augments the intrusion of salt water in these areas.
This is no exaggeration. An example of massive salt-water intrusion can be found in Villabhipur Village, where the chloride content of groundwater amounts to 5105 mg/L. Salt-water intrusion has extended to 25 km inland. In India, scientists are not as popular as politicians or cricket players, because they always make people worry!
I would like to congratulate the Central Salt & Marine Chemicals Research Institute Bhavnagar (CSMCRI) for its innovations relating to the salt industry. This organization is greatly concerned with the coastal ecosystem. Bhavnagar Bhal requires assistance to renovate the groundwater for scientists, citizens, as well as people from the private sector. All these people are interested in the social and environmental impacts of coastal changes. 30 years ago this area had a lot of species of vegetation. At present, the region is affected by pressure due to: development activities, changes linked to land use, depletion of coastal resources and degradation of coastal water quality. The physical change of this coastal area has led to social change.
The inhabitants of Kalatalav, Narmad, Kathekateli, Seney villages are crying out for fresh water.
REMOTE SENSING AND VEGETATION CHANGES: If, somebody asks why remote-sensing (IRS) images produce different results at different times, I guess this must be a joke! Let us consider the IRS-1C image of the Gujarat region, without taking into consideration recording times. The Normalized Differential Vegetation Index (NDVI)-sensor Spot XS is used to detect vegetation cover in the area. The typological analysis of the vegetation permits us to identify land salinity. In general terms, the Bhavnagar region does not have much vegetation. The northern part of Bhavnagar (Bhavnagar Bhal) is dominated by shrub vegetation, an indication of this being a saline area, whereas the southern part of Bhavnagar is an agricultural region. *************************************************************************************************************************************
FURTHER REPURCUSSIONS OF SALT WATER EXTRACTION (Bhasa Indonesia)
Pada bulan April sampai Juni 1999 saya melakukan penelitian di Bhavnagar Bhal dengan Topic : Ground Water Salinity Related Impacts and Mitigation Plans in Bhavnagar Coastal Region. Pendapat saya tentang Bhavnagar Bhal adalah : Daerah tersebut mengalami penggaraman yang hebat (heavy salinity), dengan hasil laboratorium chloride content lebih dari 1000 mg/l. Juga Salt Water Intrusion (asinya air tanah) jaraknya sudah melebihi 25 km dari pantai.
Dr. R.Sudarshana dalam tulisannya terlewatkan tentang land subsidence, hal ini pengaruh dari pemompaan air tanah dari confined sand and gravel aquifer, berkaitan dengan pemampatan tanah. Tekanan dengan turunnya permukaan air tanah, material aquifer dan lempung bertahap menjadi mampat/padat. Konsekuensi dari land subsidence (turunnya permukaan tanah) adalah bencana pada bangunan- bangunan, jalan dan beberapa infrastruktur, tidak berfungsinya saluran pembuangan, dan di pesisir (coastal region) naiknya resiko akan bencana banjir.
APA YANG AKAN TERJADI DI BHAVNAGAR BHAL ?
Dengan baiknya pasaran garam, saltpand sudah ada disekitar Kota Bhavnagar. Sumber air garam mereka pompa dari dalam tanah dengan kedalaman 122 m. Bila air tanah dipompa dari oastal aquifer melebihi kapasitas akan mengalami penurunan muka air tanah, air asin akan naik 40 m setiap m turunnya muka air tanah di coastal region. Penduduk Bhavnagar Bhal sangat bergantung air bersih dari Kota Bhavnagar, yang didistribusi dengan tanki air.
Dari hasil pengujian chloride content berindikasi telah terjadi salt water intrusion di Kota Bhavnagar. Turunnya permukaan air Waduk Bortalav (Bortalav Lake) indikasi pemompaan air tanah yang berlebihan dari kota yang berpenduduk 600 000 jiwa.
Bhavnagar dalam Lampu Kuning Salt water intrusion.
Bila seseorang bertanya kenapa citra IRS-1C yang direkam pada jam 09.00 (pagi) selalu berbeda dengan hasil rekaman pada waktu lainnya ? Itu hanya canda/guyon. Bagaimana citra IRS-1C Daerah Gujarat ? Saya akan lupakan jam perekaman. Menggunakan NDVI teknik image prosesing pilihan sensor SPOT XS, tampakan tumbuhan akan berwarna cerah, Bhavnagar Region sangat sedikit tumbuhan (vegetation). Bhavnagar bagian utara (Bhavnagar Bhal) tidak ada tumbuhan yang ada hanya belukar, indikasi saline area. Bhavnagar bagian selatan tampakan di citra lebih baik dan sangat baik untuk agriculture namun tidak tampak adanya hutan.
Akumulasi garam (penggaraman) tidak akan mengambil tempat pada sandy soil demikian juga pada "Global Salt Circulation". Setiap irrigasi menggunakan air laut akan membersihkan akumulasi garam menuju daerah yang lebih rendah dan salurah bawah tanah akan membawa garam kembali ke laut, utamanya air tanah (ground water) mengalir horisontal dengan kecepatan 1 sampai 500 m/tahun. Saya rasa problrm di Bhavnagar Bhal adalah kejenuhan tanah akan penggunaan air laut (saline water) untuk irigasi dan efek lainnya naiknya tingkat keasinan air tanah (increased ground water salinity). Pemompaan air asin dari dalam tanah untuk saltpan yang berlebihan memperluas genangan air asin didalam tanah.
Saya tidak bercanda, chloride content air tanah di Villabhipur adalah 5105 mg/l. Raksasa Salt water Intrusion. Masuknya air asin kedalam tanah sudah mencapai lebih dari 25 km dari pantai. Di India peneliti kalah populer dari pada politikus dan permainan cricket. Mungkin karena mereka selalu membuat orang was-was.
Selamat pada CSMCRI atas inovasi pembuatan garam. Instansi tersebut menaruh sangat besar perhatiannya pada lingkungan. Bhavnagar Bhal mengundang perhatian dari peneliti, warga Bhavnagar, CSMCRI dan perusahaan Garam dan orang-orang yang tertarik untuk melakukan renovasi air tanah. Saya sangat setuju akan pendapat bahwa dia hanya tertarik pada akibat terhadap masyarakat atas perubahan lingkungan pesisir, dimana 30 tahun yang lalu daerah tersebut memiliki bermacam species tanaman. Sekarang sangat kuat tekanan dari aktifitas pembangunan, perubahan penggunaan lahan, berkurangnya sumber alam pantai, dan merosotnya kualitas air tanah. Setiap tekanan pada lingkungan pesisir otomatis merubah aktifitas masyarakat didaerah tersebut.
Itu desa-desa seperti Kalatalav, Narmad, Kathekateli, Seney dsb. menangis keras memerlukan air bersih (fresh water).
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